1. Field of the Invention
This invention relates to a paper folding apparatus for folding paper along perforations and piling the same.
2. Description of the Prior Art
Generally, in a line printer, paper prefolded along perforations and contained in a paper containing box is supplied to a predetermined paper path and printed, and then discharged out of the line printer. The discharged paper is again folded along the initial perforations by a paper folding apparatus and piled.
A conventional paper folding apparatus is shown in FIG. 1 of the accompanying drawings. FIG. 1 includes paper 1 having no other lateral perforations than creases and alternately folded along these lateral perforations, a pair of paper supply rollers 2, a pair of endless conveyor belts 4 passed over a plurality of rollers 3 and disposed so as to form an inverted V-shape, a guide 5 for controlling the fold length of the paper 1, a vertically movable table 6 on which the paper may be piled, and a detector 7 such as a transmitting type photoelectric switch for detecting the folded surface of the paper 1. The detector 7 is attached to an apparatus body (not shown).
Now, when the paper is passed between the supply rollers 2 and folded into several sheets on the table 6 and set as indicated by solid line and then the folding of the paper 1 is started by rotating the supply rollers 2 and the conveyor rollers 4 in predetermined directions by a driving mechanism, not shown, the paper may sometimes assume a condition as indicated by dotted lines immediately after the folding has been started. This seems to be attributable to the fact that even if the paper is disposed at an appropriate fold angle, a sufficient friction force is not sometimes created between the paper 1 and the conveyor belts 4 and the paper is bent short of the lateral perforation 1.sub.1, and becomes "yielded".
FIG. 2 shows an example of the conventional apparatus using paper 1 having two lateral perforations at other places than creases and alternately folded along the lateral perforation 1.sub.1 having a crease. This apparatus has an inconvenience that immediately after the folding has been started, the paper 1 is folded at the lateral perforation 1.sub.2 provided at the unit of page short of the lateral perforation 1.sub.1 having a crease as indicated by dotted line and thereby causes a phenomenon of so-called "middle fold" or "reverse fold".
In FIGS. 3 to 5, the paper 1 is not initially piled on the table 6 and therefore, the table 6 is stopped at a position whereat the upper surface thereof is detected by the detector 7, and the upper surface provides the folded surface. After the paper 1 has been passed between the supply rollers 2 and set on the table 6, the folding is started.
The paper 1 is fed toward the table 6 by the supply rollers 2 and frictionally conveyed along one of the conveyor belts 4 moved round in the direction of arrow and, as soon as the paper strikes against the length controlling guide 5, it is folded along a perforation. Subsequently, the paper 1 is alternately folded at the left and right sides thereof so that it is frictionally conveyed along the other conveyor belt 4, and piled. When the folded surface is upwardly displaced due to the increased amount of pile, this displacement is detected by the detector 7 and the table 6 is lowered so as to ensure the folded surface to be always positioned at a predetermined distance from the supply rollers 2.
However, the use of the above-described conventional holding apparatus has not always resulted in good folding. One reason would be that the paper subjected to various operations in the line printer has its creases extended and it is difficult to fold the paper along the creases when it is to be folded again. Another reason is that even if the type of paper is changed, the paper folding level is always fixed and the folding corresponding to the so-called rigidity or strength peculiar to the paper is not effected.
Usually, there are six types of paper usable with the line printer, and according to JIS, they are #45, #55, #70, #90, #110 and #135. For the conventional paper folding apparatus which is designed to use exclusively the paper of quality #70, for example, among the various qualities of paper and in which the folding level is fixed, the thin paper of quality #45 or the paper of quality #110 or higher is too low or too high in rigidity or strength and it has been difficult to fold such paper well.
However, when the detector which detects the folded surface of the paper corresponding to the folding level in the conventional paper folding apparatus has been removed and the folded surface has been moved up and down, it has been found that good folding can be obtained depending on a certain position. Also, it has empirically been confirmed that the aforementioned six qualities of paper respectively have a range of folding level which enables good folding and especially, the ranges of #45 paper and #135 paper do not overlap each other. Further, the paper of #45 and #70 and the paper of #90 and #135 overlap each other in the range of folding level and therefore, at least two folding levels must be set for these qualities of paper.
Referring to FIGS. 6 and 7, there has recently been the advent of a non-impact type printer utilizing a composite technique comprising a combination of the laser light modulating technique and the electrophotographic technique, and in paper discharged from such printer, not only the creases pre-formed at the perforations disappear due to the paper being subjected to a heat treatment within the printer, but also the rigidity or strength of the paper is varied due to the paper being discharged while being hot and thus, it has been difficult to fold such paper.
The conventional paper folding apparatus, as is shown in FIG. 6, comprises a pair of paper supply rollers 2, a pair of endless conveyor belts 4 passed over a plurality of rollers 3 and disposed so as to form an inverted V-shape in which the belts are inclined at a predetermined angle with respect to the surface of paper fed in, a guide 5 for controlling the folded length of the paper 1, a paper supporting table 6, a detector 7 for detecting the folded surface of the paper 1, and a lift mechanism 8 for moving up and down the paper supporting table 6 in accordance with the output of the detector 7. Although not shown in detail, the lift mechanism 8 is provided with a rotating mechanism having its directions of normal and reverse rotation and speed of rotation controlled on the basis of the output of the detector 7, and a nut or the like threadably engaged with a screw rod 10 extending from the underside of the table 6, the nut or the like being driven by said rotating mechanism.
Initially, the paper 1 is not piled on the table 6 and therefore, the table 6 is stopped at a position whereat the upper surface thereof is detected by the detector 7, and the upper surface provides the folded surface. Then, the paper 1 is passed between the supply rollers 2 and folded into several sheets and set on the table 6, whereafter folding of the paper 1 is started by rotating the supply rollers 2 and the conveyer belts 4 in predetermined directions by a driving mechanism, not shown.
The paper 1 is fed in toward the table 6 by the supply rollers 2 and moves from a condition a to conditions b and c in succession as indicated by dots-and-dash lines, and is frictionally conveyed while bearing against the left conveyor belt 4. The paper 1 further moves to a condition d and then to a condition e, and strikes against the length controlling guide 5, whereupon the paper is folded along a perforation. Subsequently, the paper 1 is moved toward the right conveyor belt 4. This is repeated, so that the paper 1 is alternately folded at the left and right side and piled on the table.
However, when an unshown printer to which the abovedescribed paper folding apparatus is attached stops printing and the paper 1 is stopped in the condition d indicated in FIG. 6, the paper 1 subjected to a heat treatment at a high temperature within the printer is suddenly cooled and comes to have a strong curl having a small curvature. Therefore, if the printer again starts printing with the paper remaining in this condition and the paper 1 is fed in by the supply rollers, the paper 1 which has a curvature f as shown in FIG. 7 cannot be folded by the conveyor belt 4 and thus, jam of the paper will occur.
Particularly, where the paper folding apparatus is incorporated in or directly connected to the printer, the paper has no allowance for slackening and therefore, when a different size of paper is used, there is a possibility that the paper stops in the condition d within the folding apparatus depending on its size and in that case, occurrence of jam would be unavoidable.
Referring to FIGS. 8-11, the continuous paper heretofore used, if again folded, may sometimes be piled while being obliquely inclined in the direction of arrow as shown in FIG. 8 or the opposite ends of the paper may be upwardly curled as shown in FIG. 9. In the conventional folding apparatus, the phenomenon of such oblique piling or curling of the paper having the tendency to pile obliquely has been reduced by providing width guide members 12 widthwisely of the paper as shown in FIG. 10 or by providing a half-moonshaped pillow member 13 on the table as shown in FIG. 11, thereby improving the folded condition of the continuous paper. However, during the time that continuous paper of great volume is treated, the uppermost folded surface of the paper rides onto the width guide members 12 or frictionally contacts the width guide members 12 as shown in FIG. 10 or 11 and does not fall downwardly but remains caught by the width guide members, whereby smooth folding cannot take place and jam occurs sometimes as the result of unsatisfactory folding.
The cause of such oblique piling is associated with the direction of fiber of the paper created during the manufacturing step of the paper and accordingly, it would be possible to reduce the occurrence of the phenomenon of oblique piling by adjusting the direction of fiber during the manufacture of the paper. However, it is cumbersome to accurately determine the direction of fiber and further, the continuous paper discharged from a non-impact printer to which is applied the electrophotographic technique using a laser light or CRT tube is subjected to heating and pressure to have a toner image fixed within the printer and therefore, such continuous paper will suffer more remarkably from the phenomena of oblique piling and curling shown in FIGS. 8 and 9. Thus, with the conventional folding apparatus, it has been difficult to fold such continuous paper satisfactorily.